appkit:button

(appkit:button window title &key (x 20) (y 20) (width 120) (height 32) on-click)

Adds a push button with that title and frame to the window and answers it. on-click is a zero-argument function that runs on the main thread when the button is clicked (or appkit:clicked); it may call back into the GUI. Part of the appkit package, a Cocoa widget layer written in rontolisp over objc and loaded on first use: macOS (java -jar, the rontolisp binary, or a compiled .class / .jar; never a .wasm), with a display. See the macOS GUI guide.

CL-USER> (defvar *n* 0)
CL-USER> (defvar *button*
    (appkit:button *win* "Click me" :x 20 :y 40
      :on-click (lambda ()
                  (setq *n* (+ *n* 1))
                  (appkit:set-text *label* (format nil "clicked ~a time(s)" *n*)))))